Azo dyes having a high solubility in petroleum fuels

ABSTRACT

Azo dyes which are highly soluble in petroleum fuels. The dyes have the general formula ##STR1## where R 1 , R.sub. 2, R.sub. 3, and R 4  are each H or CH.sub. 3 and R.sub. 5 is either 2-ethylhexyl or 2-ethylhexyloxypropyl. When R.sub. 5 is 2-ethylhexyl, then at least one of R 1 , R 2 , R 3  and R 4  is CH 3 . When R 5  is 2-ethylhexyloxypropyl, then each of R 1 , R 2 , R 3  and R 4  is H, or at least one of R 1 , R 2 , R 3  and R 4  is CH 3  provided that R 1  and R 3  are not both CH 3  at the same time that R 2  and R 4  are each H, and provided that R 2  and R 4  are not both CH 3  at the same time that R 1  and R 3  are both H.

This application is a continuation-in-part of Ser. No. 601,015, filed Aug. 1, 1975, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to the coloration of petroleum fuels. There is a need for dyes which are quickly and highly soluble in petroleum fuels such as, for example, gasoline, diesel oils and heating and fuels oils. As is pointed out in U.S. Pat. No. 3,764,273, this need arises because of the laws of certain foreign countries which impose taxes on motive and heating oils. These laws provide that particular dyes and/or marking agents must be added to these oils to provide a means for identification to prove or disprove the payment of taxes. For example, Manitoba Regulation 51/66 under the Motive Fuel Tax Act of Canada, provides in part that "Motive fuel used for any of the purposes mentioned in subsection (7) of Section 3 of the Act shall be given a specific colour and separate identity by means of a purple dye and a chemical marker, as may be determined by the minister."

A law passed in the Federal Republic of West Germany requires the addition of certain chemicals to distillate type heating oils sold in that country after Apr. 1, 1976. These chemicals are intended to permit the identification of taxed heating oils if used illegally for much more highly taxed diesel fuels. The opportunity for fraud exists because the chemical and physical properties of heating oils and of diesel oils are quite similar.

2. Description of the Prior Art

A great variety of azo dyes have been used for many years to color gasoline and other petroleum fuels and/or distillates. These dyes have usually been solid dyes in the form of powders, flakes, granules and the like which tend to cake and which have a limited solubility and a low rate of dissolution. For instance, the solubility of the various azo dyes used in the past has been of the order of magnitude of less than about 2%, ranging upward to about 5% in some instances. Further, and most importantly, the rate of dissolution of these solid dyes in gasolines, diesel and heating oils is very slow and requires special techniques. One such special technique is the so-called "dry dye eductor" system described in U.S. Pat. No. 2,925,333. In this same patent (at Column 6) it is disclosed that the solubility test was conducted by mixing gasoline with dye "on a slowly rotating wheel for 16 hours at 80° F."

In addition, the use of powdered dyes causes (1) the evolution of noxious dye dust which exposes personnel to inhalation hazards requiring the adoption of precautionary measures and respiratory devices and (2) the deposition of dye dust on equipment and throughout the plant area requiring frequent cleanup.

Several solutions to these various problems have been suggested by the prior art. Thus, U.S. Pat. No. 3,049.533 attempts to overcome the caking and dusting problems by providing azo dyes in the form of thin platelets formed on a rotating drum.

Another solution to the problems associated with solid dyes is that of British Pat. No. 1,108,981 which solubilizes difficulty soluble solid dyes in a mixture of a liquid phenol and a hydrocarbon to provide a liquid dye. U.S. Pat. No. 3,690,809 also provides a liquid azo dyestuff by a particular combination of a mixture of azo dyes containing defined alkyl phenols or alkyl naphthols in the dye molecule together with a liquid organic viscosity depressant. Some well-known so-called "oil soluble" solid azo dyes used for coloring petroleum fuels include the following (where "C.I." refers to color index):

    ______________________________________                                          ##STR2##                                                                      SOLVENT YELLOW NO. 56      C.I. 11021                                           ##STR3##                                                                      SOLVENT YELLOW NO. 14      C.I. 12055                                           ##STR4##                                                                      SOLVENT RED NO. 24         C.I. 26105                                           ##STR5##                                                                      SOLVENT RED NO. 19         C.I. 26050                                          ______________________________________                                    

Each of the foregoing dyes presents the same disadvantages previously noted for solid dyes in general. The solubility deficiencies of Solvent Red No. 19 (C.I. 26050) will be demonstrated more fully in the Examples hereinafter set forth.

As is readily apparent, an azo dye which has excellent solubility in petroleum fuels and exhibits good storage would be desirable to remedy the defects of solid azo dyes.

Accordingly, it is an object of this invention to provide azo dyes which have high solubility in petroleum fuels and a practically instantaneous rate of dissolution therein.

It is another object of this invention to provide azo dyes which have a high rate of solubility in petroleum fuels, a practically instantaneous rate of dissolution therein, exhibit storage stability and do not adversely affect the physical and chemical characteristics of the petroleum distillate to which the are added.

SUMMARY OF THE INVENTION The present invention provides an azo dye composition having the general formula ##STR6## wherein:

A. When R₅ is 2-ethylhexyl, then at least one of said R₁, R₂, R₃ and R₄ is CH₃ ;

B. when R₅ is 2-ethylhexyloxypropyl, then each of said R₁, R₂, R₃ and R₄ is either H, or CH₃ provided that R₁ and R₃ are not both CH₃ at the same time when R₂ and R.sub. 4 are both H, or R₂ and R₄ are not both CH₃ at the same time when R₁ and R₃ are both H.

This invention also provides a colored petroleum fuel having dissolved therein a dye composition of said general formula.

The term "petroleum fuel", as used herein, means such petroleum-derived distillate products as gasoline, diesel oils, heating or fuel oils, kerosenes, jet fuels and naphthas.

The azo dyes of this invention overcome the disadvantages noted for solid dyes and possess several unique properties making them especially useful in coloring petroleum fuels. These properties are summarized as follows:

1. They are non-solids at room temperature, i.e., ranging from viscous tars to fairly mobile fluids.

2. They are highly soluble in petroleum fuels. The term "highly soluble", as used herein, means a solubility in petroleum fuels of at least about 25 percent by weight at ambient temperatures of 20° or 25° C.

3. They display a practically instantaneous rate of dissolution in petroleum fuels.

4. They display the properties of high solubility in petroleum fuels and fast rate of solubility therein under both high and low temperature conditions of storage for long periods of time.

5. They do not affect the physical or chemical properties of the petroleum fuel to which they are added.

In the instance where R₅ is 2-ethylhexyl, these azo dyes may be prepared by conventional diazotization of aminoazotoluene, or of aniline coupled to o-toluidine, or of mixed toluidines and xylidines, after which the diazotized product is coupled to 2-ethylhexylamino naphthalene. In the instance where R₅ is 2-ethylhexyloxypropyl, then aminoazobenzene is diazotized and coupled to 2-ethylhexyloxypropylamino naphthalene. Alternatively, a suitable non-solid, i.e., liquid or tarry, azo dye may be prepared in the instance where R₅ is 2-ethylhexyloxypropyl by the conventional diazotization of aniline coupled to o-toluidine or of mixed toluidines and xylidines followed by coupling to 2-ethylhexyloxypropylamino naphthalene. Surprisingly, it was found that diazotized aminoazotoluene coupled to 2-ethylhexyloxypropylamino naphthalene produced a solid dye having relatively low solubility in petroleum fuels.

One of the preferred azo dyes of this invention is where R₅ is 2-ethylhexyl and where one to two members of R₁, R₂, R₃ or R₄ is CH₃.

The compound 2-ethylhexylamino naphthalene may be prepared by the so-called Bucherer reaction as follows:

Beta-naphthol, 2-ethylhexylamine and sodium bisulfite are slurried in water and reacted in an autoclave at a temperature of 175° C. for about 12 hours. The mass is cooled, and the oil layer is separated therefrom. The oil layer is washed successively with dilute aqueous acetic acid and with hot dilute aqueous caustic soda to remove unreacted 2-ethylhexylamine and beta-napthol respectively, then dried.

In similar manner, 2-ethylhexyloxypropylamino naphthalene may be prepared by substituting 2-ethylhexyloxypropylamine for 2-ethylhexylamine.

The azo dyes of this invention may be prepared as substantially 100 % active colorants, or they may be dissolved in suitable solvents to provide color concentrates in which the active dye ranges from about 50% to about 75% by weight. Suitable solvents include but are not limited to ketones, esters, chlorinated solvents, aliphatics, aromatics such as toluene and xylene, and any of said petroleum fuels.

One of the principal distinctions between the present azo dyes and the widely used solid dye Solvent Red No. 19 is the unexpectedly high solubility in petroleum fuels of the former relative to the latter.

This is demonstrated by a series of solubility and stability tests described in the Examples hereinafter set forth using the following pairs of diesel and heating oils as exemplary of petroleum fuels:

No. 1 Heating Oil and No. 1 Diesel Oil

No. 2 Heating Oil and No. 2 Diesel Oil

No. 4 Heating Oil and No. 4 Diesel Oil

The nature of and very close to relationship between corresponding pairs of heating oils and diesel oils are indicated by their physical properties which are set forth in the following Tables 1, 2 and 3.

Looking more closely at these oils, we find that No. 1 Heating Oil is a light distillate intended for use in vaporizing type oil burners, in which oil is vaporized by contact with a heated surface or by radiation.

No. 1 Diesel Oil is a volatile distillate fuel oil for engines in service requiring frequent speed and load changes.

The specifications of these oils are set forth in Table 1.

                  TABLE 1                                                          ______________________________________                                                            No. 1     No. 1                                                                Heating   Diesel                                                                Oil       Oil                                              Flash Point (Pensky-Martens)                                                    Minimum ° F. 100         100                                           Pour Point ° F. Max.                                                                          0           --                                           Vol. % Water & Sediment                                                                             Trace       Trace                                         Carbon Residue % Max.                                                                               0.15        0.15                                          Ash Wt. %             --         0.01                                          Distillation Temp. ° F.                                                  10% Point Max.      420          --                                            90% Point Max.      550         550                                           Kinematic Viscosity cst* 100° F.                                         Min.                1.4         1.4                                            Max.                2.2         2.5                                           Cetane Number Min.    --          40                                           Gravity API Min.      35          --                                           Copper Strip Corrosion Max.                                                                         No. 2       No. 3                                         Sulfur % Max.        0.5 or legal                                                                               0.50                                          ______________________________________                                          *Centistokes                                                             

No. 2 Heating Oil is a heavier distillate than the No. 1 grade. It is intended for use in atomizing type burners which are used in most domestic and many medium capacity commercial-industrial burners.

No. 2 Diesel Oil is a distillate of lower volatility than No. 1, for engines in industrial and heavy mobile service, involving relatively high loads and uniform speeds. It forms by far the highest consumption of diesel engine oil, particularly for road vehicles. The similarity to No. 2 Heating Oil possibly creates the greatest incentive to tax frauds.

The specifications for these oils is set forth in Table 2.

                  TABLE 2                                                          ______________________________________                                                            No. 2     No. 2                                                                Heating   Diesel                                                                Oil       Oil                                              Flash Point (Pensky-Martens)                                                    Minimum ° F. 100         125                                           Pour Point ° F. Max.                                                                          20          --                                           Water & Sediment Vol. %                                                                             0.05        0.05                                          Carbon Residue       0.35        0.35                                          Ash Wt. %             --         0.01                                          Distillation Temp. ° F.                                                  10% Point Max.       --          --                                            90% Point Max.      640         640                                           Kinematic Viscosity cst 100° F.                                          Min.                2.0         2.0                                            Max.                3.6         4.3                                           Cetane Number         --         40                                            Gravity API Min.      30          --                                           Copper Strip Corrosion                                                                               --         No. 3                                         Sulfur % Max.        0.5 or legal                                                                               0.5                                           ______________________________________                                    

No. 4 Heating Oil is light residual or heavy distillate oil for use in burners which can atomize fuels of higher viscosity than domestic burners.

No. 4 Diesel Oil is a higher viscosity distillate or blend with residual oil used for constant low and medium speed engines with constant loads.

The specifications of these oils are set forth in Table 3.

                  TABLE 3                                                          ______________________________________                                                              No. 4  No. 4                                                                   Heating                                                                               Diesel                                                                  Oil    Oil                                                Flash Point (Pensky-Martens)                                                    Minimum ° F.   130      130                                            Pour Point ° F. 20       --                                             Water & Sediment Volume %                                                                              0.50     0.50                                          Carbon Residue on 10% Bottoms                                                                         --       --                                             Ash Wt. % Max.          0.10     0.10                                          Distillation Temp. :                                                                         10% Point Max.                                                                              --       --                                                       90% Point Max.                                                                              --       --                                         Kinematic Viscosity cst 100° F.                                          Min.                  5.8      5.8                                             Max.                  26.4     26.4                                           Cetane Number          --       30                                             Gravity API            --       --                                             Copper Strip Corrosion --       --                                             Sulfur % Max.          Legal    2.0                                            ______________________________________                                    

For a more complete understanding of the present invention, reference is now made to the following specific examples illustrating the novel azo dyes of this invention, their preparation and solubility characteristics.

DESCRIPTION OF THE PREFERRED EMBODIMENTS EXAMPLES 1-6 COUPLING COMPONENT 2-(2-ETHYLHEXYLAMINO) NAPHTHALENE EXAMPLE 1

In a suitable vessel, 225 grams of finely ground o-aminoazotoluene are slurried in 2000 ml water containing 1 gram non-ionic surfactant until well wetted. 2.50 grams mols HCl are added and the resultant suspension is diazotized at 15° C. with 70 grams sodium nitrite and ice as required to maintain temperature. If the sodium nitrite is not completely consumed, a little more aminoazo compound is added until reaction is complete. The finished diazo solution is filtered, the mineral acidity is removed with 210 grams 60% sodium acetate, and ice is added to give a temperature of 5° C. A solution of 280.5 grams of coupling component 2-(2-ethylhexylamino) naphthalene (100%) in 560 grams methyl alcohol is run into the diazo solution slowly with stirring. Finely dispersed bluish red dye is formed. Stirring is continued until spot tests indicate coupling is complete at which time the finished dye has condensed into a crude oily, viscous liquid to yield the product having the following formula: ##STR7## PROCEDURE A

LIQUID DYE SOLUTION

The resultant oily viscous liquid dye may be heated and taken up in an appropriate oily solvent to provide a liquid dye composition comprising 50-70% active colorant and 50-30% solvent, depending on the quantity of solvent added.

Procedure b

liquid dye - isolate

alternatively, the crude liquid dye may be taken up with a volatile solvent and the solvent removed during the drying process to yield a non-volatile liquid colorant. This may be further purified by washing with hot alcohol, decanting and drying to isolate an approximately 100% active liquid dye.

EXAMPLE 2

In a suitable vessel, 233.5 grams (dry basis) of p-aminoazobenzene hydrochloride as approximately 800 grams wet paste are slurried in 1 liter water with 1.5 gram mols HC1. Ice is added as required with 70 grams nitrite, in portions, for diazotization at 10-12° C. When complete, as indicated by total takeup of nitrous acid, the diazo solution is filtered. 280.5 grams of the coupling agaent of Example 1, 2-(2-ethylhexylamino)naphthalene (100%), are dissolved in 560 grams glacial acetic acid and are added to the diazo product after first cooling to 5° C. and removing mineral acidity with 210 grams 60% sodium acetate. The resultant dye crystallizes from oily solvents, including aromatic solvents, and diesel and heating oils. It is isolated as a crystalline solid dye at room temperature according to Procedure B of Example 1.

The product is ##STR8##

EXAMPLE 3

A slurry is made of 247.5 grams (dry basis) of the hydrochloride of the aminoazo compound resulting from the coupling of aniline to o-toluidine in 1 liter water containing 1.5 mols HC1. This mixture is diazotized with 70 grams of sodium nitrite at 0-5° C. The finished diazo product is filtered and coupled with 2-(2-ethylhexylamino) naphthalene according to the procedure of Example 1. A liquid dye is isolated by Procedure B of Example 1 and has the formula ##STR9##

EXAMPLE 4

The procedure of Example 1 is followed, except that o-toluidine is coupled to 2,5 -xylidine and the resulting aminoazo compound is diazotized. The diazo product is coupled to 2-(2-ethylhexylamino)naphthalene and the resultant liquid dye having the following formula is isolated according to Procedure B of Example 1: ##STR10##

EXAMPLE 5

The procedure of Example 1 is followed, except that a mixture of amines comprising 24% aniline, 13% mixed xylidines and 63% o-toluidine is subjected to partial diazotization and self-coupling producing mixed aminoazo compounds. The resultant mixture is diazotized according to the procedure of Example 1 and is coupled to 2-(2-ethylhexylamino)naphthalene and the resultant liquid dye is isolated according to Procedure B of Example 1 to provide a dye having, on the average, 1.78 methyl group substituents on the phenyl rings.

EXAMPLE 6

The procedure of Example 1 is followed, except that a mixture of mixed xylidine isomers is partially diazotized and self-coupled. The resultant aminoazo compound is diazotized and coupled to 2-(2-ethylhexylamino)naphthalene and the resultant liquid dye is isolated according to Procedure B of Example 1 to provide a liquid dye having four methyl group substituents on the phenyl rings.

EXAMPLE 7-12 COUPLING COMPONENT 2-(2-ETHYLHEXYLOXYPROPYLAMINO) NAPHTHALENE EXAMPLE 7

The procedure of Example 1 was followed except that the coupling component was 2-ethylhexyloxypropylamino)naphthalene and the resultant azo dye was a solid having the formula ##STR11##

EXAMPLE 8

The procedure of Example 2 was followed except that the coupling component was 2-(2-ethylhexyloxypropylamino)naphthalene and the resultant azo dye was a liquid having the formula ##STR12##

EXAMPLE 9

The procedure of Example 3 was followed except that the coupling component was 2-(2-ethylhexyloxypropylamino)naphthalene and the resultant azo dye was a tar having the formula ##STR13##

EXAMPLE 10

The procedure of Example 4 was followed except that the coupling component was 2-(2-ethylhexyloxypropylamino)naphthalene and the resultant azo dye was a tar having the formula ##STR14##

EXAMPLE 11

The procedure of Example 5 was followed except that the coupling component was 2-(2-ethylhexyloxypropylamino)naphthalene and the resultant dye was also a liquid as was the dye of Example 5.

EXAMPLE 12

The procedure of Example 6 was followed except that the coupling component was 2-(2-ethylhexyloxypropylamino)naphthalene and the resultant dye was a tar.

EXAMPLE 13

Equal quantities of each of the dyes of Examples 1-12 isolated and purified as non-volatile active colorants, were dissolved in equal quantities of No. 2 Heating Oil to provide six different dye solutions. The relative color strengths and shades of these solutions were determined and compared. The results are set forth in Table 1.

                                      TABLE 1                                      __________________________________________________________________________     COUPLING COMPONENT 2-ETHYLHEXYLAMINO NAPHTHALENE                                    Physical State                                                                          No. of CH.sub.3                                                                         %                                                             of Dye  Groups on                                                                               Relative                                                                            Relative                                           Example                                                                              at 20° C.                                                                       Phenyl Rings                                                                            Strength                                                                             Shade                                             __________________________________________________________________________     1    Liquid   2        100  Blue Red                                           2    Solid    0        121  Blue Red                                           3    Liquid   1        112  Blue Red                                           4    Liquid   3         92  Duller Blue Red                                                                than Examples                                                                  1, 2 or 3                                          5    Liquid   1.78 (Average                                                                           100  Blue Red                                           6    Liquid   4         90  Duller Blue Red                                                                than Examples                                                                  1, 2 or 3                                          7    Solid    2        100  Blue Red                                           8    Liquid   0        103  Yellower Red                                       9    Tar      1         97  Blue Red                                           10   Tar      3         90  Bluer Red                                          11   Liquid   1.78 (Average)                                                                           96  Blue Red                                           12   Tar      4         90  Yellower Red                                       __________________________________________________________________________

The foregoing results show the following with respect to the azo dyes of the present invention, as represented by the general formula: ##STR15##

1. When R₅ is 2-ethylhexyl, then non-solid dyes are obtained when at least one of said R₁, R₂, R₃ and R₄ substituents is CH₃.

2. When R₅ is 2-ethylhexyloxypropyl, then non-solid dyes are obtained when:

A. r₁, r₂, r₃ and R₄ are each H;

B. r₁, r₂, r₃ and R₄ are each CH₃ provided that R₁ and R₃ and not both CH₃ at the same time when R₂ and R₄ are both H;

C. r₁, r₂, r₃ and R₄ are each CH₃ provided that R₂ and R₄ are not both CH₃ at the same time when R₁ and R₃ are both H.

EXAMPLE 14

Each of the isolated and purified dyes of Examples 1-12 was dissolved in the following fuels in the proportion of 58% by weight of dye and 42% by weight of fuel:

No. 1 Heating Oil

No. 2 Heating Oil

No. 4 Heating Oil

No. 1 Premium Diesel Oil

No. 2 Premium Diesel Oil

No. 2 Regular Grade Diesel Oil

Each dye-fuel oil mixture was warmed with stirring and then cooled to 25° C. The solid dyes of Examples 2 and 7 precipitated as a solid mass almost immediately upon cooling to 25° C. whereas the dyes of Examples 1, 3, 5 and 8 were completely soluble and remained soluble at temperatures ranging from -10° C. to 25° C. The dyes of Examples 4, 6, 9, 10, 11 and 12 all displayed some separation of dye upon lengthy storage, although equilibrium solubilities of each dye exceeded 25 percent by weight.

EXAMPLE 15

Solvent Red No. 19 was subjected to the same solubility test as set forth in Example 14. In each case where the dye-fuel oil mixture was warmed and then cooled to 25° C. precipitation occurred immediately.

In each instance, the precipitated mass was filtered and the dye content of the filtrate was determined colorimetrically. The results were as follows:

    ______________________________________                                                          Red No. 19                                                                     % by Weight                                                                    Soluble                                                       Fuel             (At Equilibrium)                                              ______________________________________                                         No. 1 Heating Oil                                                                               2.23                                                          No. 2 Heating Oil                                                                               3.41                                                          No. 4 Heating Oil                                                                               5.76                                                          No. 1 Premium Diesel                                                                            1.89                                                          No. 2 Premium Diesel                                                                            2.30                                                          No. 2 Regular Diesel                                                                            2.63                                                          ______________________________________                                    

EXAMPLES 16-28

Aminoazobenzene was diazotized according to the procedure of Example 1 and then coupled to each of a series of aminonaphthalene compounds having the formula ##STR16## to give a dye of the general formula ##STR17## in which R₅ is as indicated and the physical state of the resulting dye after isolation according to Procedure B of Example 1 is as set forth in Table 2.

                  TABLE 2                                                          ______________________________________                                                                    Physical State                                      Example  R.sub.5           of Dye                                              ______________________________________                                         16      Ethyl              Solid                                               17      n-Butyl            Solid                                               18      Methoxypropyl      Solid                                               19      Hydroxyethylethoxy Solid                                               20      n-Hexyl            Solid                                               21      Cyclohexyl         Solid                                               22      Ethoxyethoxypropyl Solid                                               23      n-Heptyl           Solid                                               24      n-Octyl            Solid                                               25      2-Ethylhexyl       Solid                                               26      n-Decyl            Solid                                               27      2-Ethylhexyloxypropyl                                                                             Liquid                                              28      n-Dodecyl          Solid                                               ______________________________________                                    

As in evident, it was found that all of the foregoing dyes were solid materials with the exception of the dye of Example 27 which is a liquid. Thus, in Examples 16-28, where there are no CH₃ groups on the phenyl rings, the only liquid dye of this series is where R₅ is 2-ethylhexyloxypropyl.

EXAMPLES 29-41

Aminoazotoluene was diazotized according to the procedure of Example 1 and the coupled to each of a series of aminonaphthalenes having a formula ##STR18## to give a dye of the general formula ##STR19## in which R₅ is as indicated and the physical state of the resulting dye after isolation according to Procedure B of Example 1 is as set forth in Table 3.

                  TABLE 3                                                          ______________________________________                                                                     Physical State                                     Example    R.sub.5          of Dye                                             ______________________________________                                         29        Ethyl             Solid                                              30        n-Butyl           Solid                                              31        Methoxypropyl     Solid                                              32        Hydroxyethylethoxy                                                                               Solid                                              33        n-Hexyl           Solid                                              34        Cyclohexyl        Solid                                              35        Ethoxyethoxypropyl                                                                               Solid                                              36        n-Heptyl          Solid                                              37        n-Octyl           Solid                                              38        2-Ethylhexyl      Liquid                                             39        n-Decyl           Solid                                              40        Ethylhexyloxypropyl                                                                              Solid                                              41        n-Dodecyl         Solid                                              ______________________________________                                    

It is seen that in the instance where there is a CH₃ group on each of the phenyl rings, then only the dye of Example 38 is a liquid dye. This was surprising and unexpected in view of the fact that adjacent homologs, the n-heptyl and n-octyl derivatives, are solid dyes.

EXAMPLES 42-93

The solubility properties of each of the dyes of Examples 16-41 were evaluated in the fuels No. 1 and No. 2 Heating Oils, respectively. The procedure was as follows:

Where the dyes are solid dyes, excess of pulverized solid dye, far beyond that which would dissolve, i.e., 30 to 35% dye, was added to the respective oils at 25° C. and agitated at constant speed. Samples were removed at 1, 10 and 20 minute intervals, filtered, and the amount of dissolved dye determined colorimetrically.

The tarry non-solid dyes were charged in proportions of 50-60% dye to 50-40% oil rather than 30-35% used for the solid dyes. In fact, it was very difficult to stir the tarry dye-fuel oil mixture at a dye concentration of 50%. Samples for these dyes were taken after 2 minutes. The longer initial time for the tarry dyes was to permit reasonable contact between solvent and the viscous, condensed dye. The liquid dye resulting from coupling diazotized aminoazobenzene to 2-(2-ethylhexyloxypropyl)aminonaphthalene, i.e., the dye of Example 27, and the liquid dye resulting from coupling diazotized aminoazotoluene to 2-(2-ethylhexylamino)naphthalene, i.e., the dye of Example 38, dissolved completely after two minutes contact was the heating oils.

The dye resulting from the reaction of diazotized aminoazobenzene and 2-(ethoxyethoxypropylamino)naphthalene (the dye of Example 22) is a tar which is essentially mobile at room temperature but displays low solubility in both fuels much like that of a solid dye, and is therefore classified as such. The quantitative solubilities observed are set forth in Tables 4, 5, 6 and 7.

                                      TABLE 4                                      __________________________________________________________________________                     No. 1 Fuel Oil - Aminoazobenzene Dyes                                          Percent Dissolved                                              Example                                                                              R.sub.5   1 Minute  10 Minutes                                                                            20 Minutes                                    __________________________________________________________________________     42   Ethyl      1.05      1.36   1.48                                          43   n-Butyl    1.99      1.79   1.57                                          44   Methoxypropyl                                                                             2.02      3.15   3.57                                          45   Hydroxyethylethoxy                                                                        0.06      0.06   0.06                                          46   n-Hexyl    4.65      4.47   4.35                                          47   Cyclohexyl 4.01      2.25   2.30                                          48   Ethoxyethoxypropyl                                                                        3.68      --     3.68                                          49   n-Heptyl   4.92      7.83   7.56                                          50   n-Octyl    12.05     7.26   5.96                                          51   2-Ethylhexyl                                                                              3.43      3.87   4.47                                          52   n-Decyl    4.97      5.12   5.63                                          53   Ethylhexyloxypropyl                                                                       52.3 (2min.)                                                                             --     52.3                                          54   n-Dodecyl  2.85      4.60   5.38                                          __________________________________________________________________________

                                      TABLE 5                                      __________________________________________________________________________                     No. 2 Fuel Oil - Aminoazobenzene Dyes                                          Percent Dissolved                                              Example                                                                              R.sub.5   1 Minute  10 Minutes                                                                            20 Minutes                                    __________________________________________________________________________     55   Ethyl      1.49      1.64   1.78                                          56   n-Butyl    1.83      2.03   2.12                                          57   Methoxypropyl                                                                             0.66      0.68   0.73                                          58   Hydroxyethylethoxy                                                                        0.14      0.17   0.21                                          59   n-Hexyl    5.12      5.12   5.27                                          60   Cyclohexyl 3.10      3.10   3.21                                          61   Ethoxyethoxypropyl                                                                        0.57      0.58   0.61                                          62   n-Heptyl   7.11      8.10   8.90                                          63   n-Octyl    5.48      6.25   6.25                                          64   2-Ethylhexyl                                                                              4.63      4.90   5.13                                          65   n-Decyl    6.36      7.25   8.14                                          66   Ethylhexyloxypropyl                                                                       52.3 (2 min.)                                                                            --     52.3                                          67   n-Dodecyl  7.46      8.17   9.06                                          __________________________________________________________________________

The foregoing results set forth in Tables 4 and 5 demonstrate that the solid dyes have relatively limited solubility in fuel oils, whereas the single liquid dye (where R₅ is ethylhexyloxypropyl - see Examples 53 and 66) displays exceptionally high solubility.

                                      TABLE 6                                      __________________________________________________________________________                     No. 1 Fuel Oil - Aminoazotoluene Dyes                                          Percent Dissolved                                              Example                                                                              R.sub.5   1 Minute  10 Minutes                                                                            20 Minutes                                    __________________________________________________________________________     68   Ethyl      0.24      0.32   0.37                                          69   n-Butyl    0.19      0.26   0.26                                          70   Methoxypropyl                                                                             0.58      0.57   0.58                                          71   Hydroxyethylethoxy                                                                        0.09      0.12   0.13                                          72   n-Hexyl    1.31      1.28   1.27                                          73   Ethoxyethoxypropyl                                                                        5.33      6.23   7.40                                          74   Cyclohexyl 0.82      0.87   0.94                                          75   n-Heptyl   1.42      1.56   1.65                                          76   n-Octyl    1.38      1.39   1.78                                          77   2-Ethylhexyl                                                                              58.0 (2 min)                                                                             --     58.0                                          78   n-Decyl    1.09      1.13   1.14                                          79   Ethylhexyloxypropyl                                                                       6.44      7.41   8.35                                          80   n-Dodecyl  3.29      4.04   4.50                                                          No. 2 Fuel Oil - Aminoazotoluene Dyes                                          Percent Dissolved                                              Example                                                                              R.sub.5   1 Minute  10 Minutes                                                                            20 Minutes                                    __________________________________________________________________________     81   Ethyl      0.29      0.37   0.39                                          82   n-Butyl    0.27      0.29   0.35                                          83   Methoxypropyl                                                                             2.96      4.21   4.96                                          84   Hydroxyethylethoxy                                                                        0.20      0.15   0.15                                          85   n-Hexyl    0.93      1.01   1.11                                          86   Ethoxyethoxypropyl                                                                        3.70      --     3.97                                          87   Cyclohexyl 0.99      1.05   1.09                                          88   n-Heptyl   1.77      2.27   2.59                                          89   n-Octyl    2.26      2.89   2.69                                          90   2-Ethylhexyl                                                                              55.3 (2 min)                                                                             --     55.3                                          91   n-Decyl    1.30      1.37   1.48                                          92   Ethylhexyloxypropyl                                                                       6.12      6.85   7.71                                          93   n-Dodecyl  4.48      4.68   5.21                                          __________________________________________________________________________

The foregoing results set forth in Tables 6 and 7 demonstrate that the solid dyes have relatively limited solubility in fuel oils whereas the single liquid dye (where R₅ is 2-ethylhexyl - see Examples 77 and 90) displays exceptionally high solubility.

EXAMPLE 94

The isolated and purified dyes of Examples 1-6, where R₅ is 2-ethylhexyl, were dissolved by warming with agitation in No. 1 Heating Oil in the proportions of 50 to 60% dye in 50 to 40% of the petroleum fuel. The resultant mixtures were stored at ambient temperatures (20° to 25° C.) and at -10° C. Where any separation of dye occurred, the dye content of the remaining solution was determined colorimetrically. The results are shown in Table 8.

                  TABLE 8                                                          ______________________________________                                         NO. 1 HEATING OIL                                                              Dye of           Number     Solubility (% by Wt.)                              Example                                                                              R.sub.5    CH.sub.3 Groups                                                                           (20° C.-25° C.)                                                            -10° C.                           ______________________________________                                         1     2-ethylhexyl                                                                              2          Complete  Complete                                 2     2-ethylhexyl                                                                              0           4.4      --                                       3     2-ethylhexyl                                                                              1          Complete  Complete                                 4     2-ethylhexyl                                                                              3          44.8      --                                       5     2-ethylhexyl                                                                              1.78(average)                                                                             Complete  Complete                                 6     2-ethylhexyl                                                                              4          46.6      --                                       ______________________________________                                    

EXAMPLE 95

The procedure of Example 94 was repeated except that the petroleum fuel was No. 2 Heating Oil. The results are set forth in Table 9.

                  TABLE 9                                                          ______________________________________                                         NO. 2 HEATING OIL                                                              Dye of           Number     Solubility (% by Wt.)                              Example                                                                              R.sub.5    CH.sub.3 Groups                                                                           (20° C.-25° C.)                                                            -10° C.                           ______________________________________                                         1     2-ethylhexyl                                                                              2          Complete  Complete                                 2     2-ethylhexyl                                                                              0           5.1      --                                       3     2-ethylhexyl                                                                              1          Complete  Complete                                 4     2-ethylhexyl                                                                              3          44.1      --                                       5     2-ethylhexyl                                                                              1.78(average)                                                                             Complete  Complete                                 6     2-ethylhexyl                                                                              4          45.7      --                                       ______________________________________                                    

EXAMPLE 96

The procedure of Example 94 was repeated except that the dyes of Examples 7-12 were used and the petroleum fuel was No. 1 Heating Oil. The results are set forth in Table 10.

                                      TABLE 10                                     __________________________________________________________________________     NO. 1 HEATING OIL                                                              Dye of         Number  Solubility (% by Wt.)                                   Example                                                                               R.sub.5                                                                               CH.sub.3 Groups                                                                         (20° C.-25° C.)                                                            -10° C.                                __________________________________________________________________________      7   2-ethylhexyloxy-                                                                        2 (R.sub.1 and R.sub.3                                                                   8.3      --                                                  propyl  are both CH.sub.3)                                                8   2-ethylhexyloxy-                                                                        0        Complete  Complete                                            propyl                                                                    9   2-ethylhexyloxy-                                                                        1        26.6       9.5                                                propyl                                                                   10   2-ethylhexyloxy-                                                                        3        29.5      19.8                                                propyl                                                                   11   2-ethylhexyloxy-                                                                        1.78(average)                                                                           41        24.7                                                propyl                                                                   12   2-ethylhexyloxy-                                                                        4        31        17.0                                                propyl                                                                   __________________________________________________________________________

EXAMPLE 97

The procedure of Example 94 was repeated except that the dyes were those of Examples 7-12 and the petroleum fuel was No. 2 Heating Oil. The results are set forth in Table 11.

                                      TABLE 11                                     __________________________________________________________________________     NO. 2 HEATING OIL                                                              Dye of          Number Solubility (% by Wt.)                                   Example                                                                               R.sub.5                                                                               CH.sub.3 Groups                                                                         (20° C.-25° C.)                                                            -10° C.                                __________________________________________________________________________      7   2-ethylhexyloxy-                                                                        2 (R.sub.1 and R.sub.3                                                                   7.7      --                                                  propyl  are both CH.sub.3)                                                8   2-ethylhexyloxy-                                                                        0        Complete  Complete                                            propyl                                                                    9   2-ethylhexyloxy-                                                                        1        28.8       9.5                                                propyl                                                                   10   2-ethylhexyloxy-                                                                        3        29.7      12.1                                                propyl                                                                   11   2-ethylhexyloxy-                                                                        1.78(average)                                                                           40        24.2                                                propyl                                                                   12   2-ethylhexyloxy-                                                                        4        28.3      19.7                                                propyl                                                                   __________________________________________________________________________

The following conclusions may be drawn from the results of Examples 1-97:

1. Where the R₅ substituent is 2-ethylhexyl and there is at least one methyl substituent on the phenyl rings, i.e., where at least one of R₁, R₂, R₃ and R₄ is CH₃, then:

A. non-solid dyes in the form of liquids or tars are obtained.

B. such dyes have a high solubility in petroleum fuels.

2. Where the R₅ substituent is 2-ethylhexyloxypropyl, then:

Non-solid dyes, in the form of liquids or tars, which are highly soluble in petroleum fuels are obtained when either (A) each of R₁, R₂, R₃ and R₄ is hydrogen, or (B) each of R₁, R₂, R₃ or R₄ is CH₃, provided that R₁ and R₃ are not both CH₃ at the same time when R₂ and R₄ are both H, or (C) each of R₁, R₂, R₃ and R₄ is CH₃, provided that R₂ and R₄ are not both CH₃ at the same time when R₁ and R₃ are both H.

3. The solubility in various petroleum fuels and of the azo dyes of the present invention is remarkably and surprisingly high when compared with the solid dyes of similar chemical structure.

EXAMPLE 98

To demonstrate that the azo dyes of this invention have a much lesser solubility in petroleum fuels than in xylene, a conventionally used aromatic solvent, each of the dyes of Examples 1-12 was dissolved by warming with agitation in xylene in the proportions of 50-60% dye and 50 to 40% xylene. The solutions obtained were stored at 20°-25° C. and at -10° C. Where any separation of dye occurred, the dye content of the remaining solution was determined colorimetrically. The results are shown in Table 12.

                  TABLE 12                                                         ______________________________________                                         XYLENE                                                                         Dye of                 Solubility (% by Wt.)                                   Example                                                                                 R.sub.5       (20° C.-25° C.)                                                               -10° C.                             ______________________________________                                         1      2-ethylhexyl    Complete     Complete                                   2      2-ethylhexyl    25.5         10.35                                      3      2-ethylhexyl    Complete     Complete                                   4      2-ethylhexyl    50.0         25.0                                       5      2-ethylhexyl    Complete     Complete                                   6      2-ethylhexyl    43.5         37.5                                       7      2-ethylhexyloxypropyl                                                                          Complete     20.8                                       8      2-ethylhexyloxypropyl                                                                          Complete     Complete                                   9      2-ethylhexyloxypropyl                                                                          Complete     38.1                                       10     2-ethylhexyloxypropyl                                                                          36.3         20.8                                       11     2-ethylhexyloxypropyl                                                                          Complete     43.5                                       12     2-ethylhexyloxypropyl                                                                          42.8         35.7                                       ______________________________________                                    

The present invention, therefore, provides azo dyes which have a high solubility in petroleum fuels and overcome the noted deficiencies of prior art solid azo dyes. 

What is claimed is:
 1. An azo dye having a high solubility in petroleum fuels and having the formula ##STR20## in which R₁, R₂, R₃ and R₄ are each H or CH₃ and R₅ is either 2-ethylhexyl or 2-ethylhexyloxypropyl, wherein:A. when R₅ is 2-ethylhexyl, then at least one of said R₁, R₂, R₃ and R₄ is CH₃ ; B. when R₅ is 2-ethylhexyloxypropyl, then each of said R₁, R₂, R₃ and R₄ is either, H or CH₃ provided that R₁ and R₃ are not both CH₃ at the same time when R₂ and R₄ are both H, or R₂ and R₄ are not both CH₃ at the same time when R₁ and R₃ are both H.
 2. An azo dye of claim 1 wherein R₁ or R₂ is CH₃ and R₅ is 2-ethylhexyl.
 3. An azo dye of claim 1 wherein R₃ or R₄ is CH₃ and R₅ is 2-ethylhexyl.
 4. An azo dye of claim 1 wherein R₁ and R₂ are each CH₃ and R₅ is 2-ethylhexyl.
 5. An azo dye of claim 1 wherein R₃ and R₄ are each CH₃ and R₅ is 2-ethylhexyl.
 6. An azo dye of claim 1 wherein R₁ and R₃ are each CH₃ and R₅ is 2-ethylhexyl.
 7. An azo dye of claim 1 wherein R₂ and R₄ are each CH₃ and R₅ is 2-ethylhexyl.
 8. An azo dye of claim 1 wherein R₁, R₃ and R₄ are each CH₃ and R₅ is 2-ethylhexyl.
 9. An azo dye of claim 1 wherein R₁, R₂, R₃ and R₄ are each CH₃ and R₅ is 2-ethylhexyl.
 10. An azo dye having a high solubility in petroleum fuels and having the formula ##STR21## in which R₁, R₂, R₃ and R₄ are each H or C₃ with the proviso that at least one of said R₁, R₂, R₃ and R₄ is CH₃.
 11. The azo dye of claim 10 wherein R₁ is CH₃.
 12. The azo dye of claim 10 wherein R₂ is CH₃.
 13. The azo dye of claim 10 wherein R₃ is CH₃.
 14. The azo dye of claim 10 wherein R₄ is CH₃.
 15. An azo dye having a high solubility in petroleum fuels and having the formula ##STR22## in which each of R₁, R₂, R₃ and R₄ is H or CH₃, with the proviso that R₁ and R₃ are not both CH₃ at the same time when R₂ and R₄ are both H, and R₂ and R₄ are not both CH₃ at the same time when R₁ and R₃ are both H.
 16. The azo dye of claim 15 wherein each of said R₁, R₂, R₃ and R₄ is H.
 17. The azo dye of claim 15 wherein each of said R₁, R₂, R₃ and R₄ is CH₃.
 18. A colored petroleum fuel having dissolved therein an azo dye composition having the general formula ##STR23## in which R₁, R₂, R₃ and R₄ are each H or CH₃ with the proviso that at least one of said R₁, R₂, R₃ and R₄ is CH₃.
 19. A colored petroleum fuel having dissolved therein an azo dye composition having the formula ##STR24## in which each of R₁, R₂, R₃ and R₄ is H or CH₃, with the proviso that R₁ and R₃ are not both CH₃ at the same time when R₂ and R₄ are both H, and R₂ and R₄ are not both CH₃ at the same time when R₁ and R₃ are both H.
 20. The colored petroleum fuel of claim 19 wherein each of said R₁, R₂, R₃ and R₄ is H.
 21. The colored petroleum distillate of claim 19 wherein each of said R₁, R₂, R₃ and R₄ is CH₃. 